The present invention relates to a printhead of an ink jet printing apparatus and its manufacturing method and, more particularly, to a printhead and its manufacturing method of forming ink orifices on a photosensitive film by photolithography (exposure and development).
In a conventional thermal bubble printhead, a high temperature is generated by a heating element so that a bubble is generated in the ink within the ink chamber on the heating element. The ink is ejected through an ink orifice by the pressure of the bubble and a dot of ink is printed onto a substrate (such as a sheet of paper). However, to let the bubbles generated by heating adequately eject the ink and form a dot of ink, the ink has to be confined in the ink chamber of the printhead and has to be ejected through a predetermined ink orifice.
A piezoelectric printhead utilizes a piezoelectric material to eject the ink by deforming a film through changing the voltage of an electrode so that the ink is ejected by the film and a dot of ink is printed onto a predetermined substrate through an ink orifice.
The print cartridge of a conventional bubble-type ink jet printing apparatus is shown in FIG. 1. It comprises an ink reservoir 10 and a printhead 12. The ink in the ink reservoir 10 flows through the printhead 12 and is ejected by the printhead 12 onto a substrate. FIG. 2 illustrates the structure of the printhead 12. The printhead 12 comprises a micro-control apparatus 16 formed with a plurality of ejecting elements (i.e. heating elements 14 in accordance with the preferred embodiment of the invention). A photosensitive film (dry film photoresist) 18 is formed on the micro-control apparatus 16. The photosensitive film 18 is used to form ink chambers 20 at locations in alignment with the heating elements 14 by photolithography (exposure and development) so that the ink can flow into the ink chambers 20. The ink orifices 22 is formed in a nozzle plate 24 by electrical forming and the nozzle plate 24 is applied to the dry film photoresist 18 by a way of precision alignment. Therefore, in the assembling process, the ink orifices 22 in the nozzle plate 24 must be in precision alignment with the ink chambers 20 in the photosensitive film 18 respectively so that the ink heated by the heating elements 14 can be ejected through the ink orifices 22. It can be known that this manufacturing process incurs high costs including the tool cost for precision alignment and low quality alignment, assembling, or application of the nozzle plate 24 to the dry film photoresist 18 reduces the yield rate.
Another printhead of a bubble-type ink jet printing apparatus is disclosed in U.S. Pat. No. 5,537,133 and is illustrated in FIG. 3. The printhead 30 comprises a micro-control apparatus 34 formed with a plurality of ejecting elements (i.e. heating elements 32 in accordance with the preferred embodiment of the invention). A photosensitive film (dry film photoresist) 35 is formed on the micro-control apparatus 34. An ink chamber 36 is formed on each of the heating elements 32 by photolithography (exposure and development). Ink orifices 39 are formed in a tape (flexible circuit board) 38, which is attached to the printhead 30 by Tape Automated Bonding (TAB), by laser ablating and the tape 38 is applied to the micro-control apparatus 34 in a way of precision alignment so that each ink orifice 39 and a corresponding ink chamber 36 cooperatively form an ink reservoir for the ink. However, forming ink orifices 39 in tape 38 by laser ablating incurs a high equipment cost that significantly increases the manufacturing cost of the printhead. In addition, low quality alignment and assembling may also reduce the yield rate.
A primary object of the invention is to provide a printhead and the manufacturing method therefor to thereby prevent ink channels and ink chambers provided in a first layer of film from adhering to a nozzle plate formed by photolithography when the nozzle plate is applied to the first layer of film.
Another object of the invention is to provide a printhead and the manufacturing method therefor to thereby make an electrical connection between signal input means and a micro-control apparatus.
Still another object of the invention is to provide a printhead and the manufacturing method therefor that features the efficacy of precision alignment and high quality assembling so that the yield can be increased and the manufacturing process can be simplified.
Further still another object of the invention is to provide a printhead and the manufacturing method therefor so that the process of manufacturing a printhead can be simplified, the equipment cost can be reduced, and the yield can be increased.
A printhead of an ink jet printing apparatus according to the present invention comprises a micro-control apparatus formed with a plurality of ejecting elements; a first layer of film, formed over said micro-control apparatus, with a plurality of ink chambers formed at positions respectively corresponding to said plurality of ejecting elements, a plurality of ink channels connected with said plurality of ink chambers, and a plurality of supporting cylinders located within said plurality of ink channels; a photosensitive film, formed over said first layer of film, with a plurality of ink orifices formed at positions respectively corresponding to said plurality of ink chambers by photolithography; and a signal input means connected to connected to said micro-control apparatus.
Therefore, the manufacturing process of the printhead in accordance with the present invention is relatively simple. Using this process, the application of a nozzle plate to a photoresist film and the precision alignment between ink orifices and ink chambers in manufacturing a conventional printhead can be avoided so that the throughput and yield rate can be increased.